A true understanding of cellular biology, and of therapeutic effects on pathological conditions under a variety of experimental conditions, requires the noninvasive monitoring of metabolism. Nuclear magnetic resonance (NMR) methods enable metabolism to be studied non-invasively. We have developed a cell perfusion technique allowing the effective application of NMR methods to cell lines grown in culture. This technique consists of embedding cells in a neutral agarose gel thread (0.5 mm) allowing continuous perfusion and rapid diffusion of metabolites into the cells. The method is applicable to any cells, including anchorage-independent cells, and to any NMR spectrometer. We are currently applying 31P, 1H and 13C NMR to study the metabolism of normal and cancerous cells and the effects of perturbants, such as heat and drugs, upon them.